Electron discharge device thermionic cathode having reduced operating temperature and method of making same

ABSTRACT

Reduction of thermionic cathode operating temperature is accomplished by the inclusion in the emissive coating of amounts of nickel coated carbonates which can ordinarily vary between more than 0 percent and up to about less than 25 percent by weight of the emissive material without adversely effecting emission. The nickel coated carbonates contain from about 2 percent to about 7 percent by weight nickel.

United States Patent Inventors: William E. Buescher; Donald R. 1 Kerstetter, both of Emporium,Pa.

Assignee: GTE Syl ania Incorporated Filed: June 30,1971

App]. No.: 158,157

Buescher et al. [451 a. 17, 1972 [5 ELECTRON DISCHARGE DEVICE [56] References Cited THERMIONIC CATHODE HAVING 1 REDUCED OPERATING UN TED STATES PATENTS TEMPERATURE AND METHOD 1 3,615,901 1971 Medicus ..1 17/223 MAKING SAME I 3,393,090 7/1968 Barraco ..1 17/223 Primary Examiner- -Da id Schonberg Assistant Examiner-Paul A. Sacher Attorney-Donald R. Castle et a].

[57] ABSTRACT Reduction of thermionic cathode operating temperature is accomplished by the inclusion in the emissive "313/346 1 17/223 252/513 coating of amounts of nickel coated carbonates which Int Cl gi /i; can ordinarily vary between more than 0 percent and Field of Search ..|17/223; 2s2/s13,'s21; '7 P percent by 9 I emissive material without adversely effecting emission.

313/346 R, 346 DC The mckel coated carbonates contain from about 2 percent to about 7 percent by weight nickel.

I 1 Claim, 1 Drawing Figure 880-- p aso-\ s4o- 3 820-- a eoo-- D. I E 780- J 760- e I 740 2 72o-- u n o 6.25 |2.5- 25 Y 7: NCC IN EMlSSlON COATING lOO ( 2 a, N1 BY WEIGHT OF CARBONATES) P'ATENTEDum 11 m2 hmwzzommdpmo E05; 3 z NV 3 OE 68. 22. 03 dmw INVENTORS WILLIAM E. BUESCHER & DONALD R. KERSTETTER 3 ATTORNEY TEMPERATURE AND METHOD OF MAKING sAME BACKGROUND OF THE INVENTION This invention relates to thermionic cathodes for electron discharge devices and more particularly to such cathodes having reduced operating temperatures and tomethods of making the same.

It frequently happens that a more or less standard design of electron discharge device develops a cathode temperature that is too high for optimum operation of the device in accordance with some prerequisite and arbitrary standard. The condition may manifest itself in many ways, one of which is emission from the control grid at the elevated temperatures. Such a condition frequently results in the inoperability of the device for the purpose for which it was designed. The reason for the higher temperature may stem from numerous causes such as a change in materials or faulty initial design. Prior techniques for correcting such a condition included changing the heater, redesigning the cathode to provide greater radiation area, or redesigning the grid to use larger lateral wires to increase heat radiation therefrom and lower the temperature to below that at which emission would occur. All of these above solutions, while workable in some instances, prove expensive, change other tube operating characteristics; or make the tube less reliable; therefore, it would prove advantageous if a simple, inexpensive solution to this problem could be found.

. OBJECTS AND SUMMARY OF THE INVENTION It is, therefore, an object of this invention to obviate the disadvantages of the prior art. It is a further object of this invention to provide a unique and simple method of reducing. cathode operating temperature. I

It is another object of the invention to provide a method of reducing cathode operating temperature without introducing-any inert materials.

These objects are accomplished in one aspect of the invention by the provision of nickel coated carbonates as part of the emissive material. The presence of the nickel coated carbonates increases the thermal emissivity of the cathode thereby lowering the temperature under the same operating characteristics of heater voltage and current. v

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE represents a graph of temperature drop vs'percent ofnickel coated carbonates in the emissive material.

DESCRIPTION or THE PREFERRED EMBODlMENTS centage of nickel coated carbonates (NCC) contained in the emissive material. The tests were conducted upon 6LR6 cathodes containing from 0% NCC (as a control) and groups containing 6.25, 12.5, 25, and 100 percent NCC respectively. While increasing the amount of NCC to 100 percent of the emissive material continually adds'to the temperature drop, it will be seen that the greatestdrop occurs in the range of NCCs up to 25 percent. This is also the practical limit for correcting for an overheating cathode since the temperature tolerance for the originally designed operating parameters would probably be exceeded by further increases in the percentage of N CC. Table I below indicates this data in tabular form.

Study of the tabular data show "that as the amount of NCCs is increased, the cathode temperature drops and the thermal emissivity or radiation of the cathode increases. It can also be seen that the heater temperature drops, resulting in a drop in heater resistance and a corresponding increase in wattage to the heater; the table shows this increase as well as the percent changes. If readings would have been made on the basis of constant wattage, then the temperature differential at 6.3,, would be greater than 155C. f

This process lends itself to ease of duplication and predictability of temperature drop. As will be seen from a study of the graph represented in the single Figure, the actual equation representing the temperature drop from 0 percent NCCs to 100 percent NCCs would be exponential; however, an approximate linear equation can be employed for the range of 0 percent to 25 percent NCCs with which the instant invention is particularly concerned, this equation being: (for 2 percent Ni by wt. of carbonates) per percent of NCC. Utilization of this formula makes 1 it a simple matter to determine the: amount of NCCs to be employed to produce a given temperature reduction. Similar formulas are easily derived for other concentrations of nickel by plotting graphs from observed data.

The percent nickel on the carbonates can vary I between about 2 percent and 7 percent by weight of the carbonates. Tests results indicate that below 2 percent the temperature drop is small and above 7 percent the material begins to lose emissive sely effecting the cathode.

The NCCs can be added to the regular carbonates in any conventional manner and the combination can be applied to cathodes by known techniques, such as spraying from a suspension.

properties, thus adver NCCs are available from GTE Sylvania Corporation, ChemicalandvMetallurgical Division, Towanda, Pennsylvania.

Thus, it will be seen that there is herein provided new and-novel method of achieving a temperature reduc-' tion as defined by the appended claims.

We claim: 1. A thermionic electron discharge device cathode comprising: an active nickel substrate containing therein an electron emissive material consisting essentially of combinations of barium, strontium and calcium carbonates, and from about above 0 percent to about less than 25 percent of nickel coated carbonates, said nickel being present in an amount equal to about 2 percent to 7 percent by weight of said nickel coated carbonates, said carbonates having said nickel coating being the same as the carbonates of said emissive material. 

